Process of drawing for bulky yarn



Aug. 11, 1964 P. T. SCOTT 3,143,784

PROCESS OF DRAWING FOR BULKY YARN I Filed July 5, 1962 INVENTOR PAUL T.SCOTT WZM ATTORNEY United States Patent 3,143,784 PROCESS OF DRAWING FOREULKY YARN Paul T. Scott, Kinston, N11, assignor to E. i. du Pont deNemours and Company, Wilmington, DeL, a corporation of Delaware FiledJuly 5, 1962, Ser. No. 207,654 5 Claims. (Cl. 2872) This inventionrelates to a process for drawing continuous filament yarn and, moreparticularly, to a process for drawing bulked crimped filament yarn fromcontinuous synthetic linear polymer filaments.

Artificial fibers are normally produced most easily as continuousfilaments. These continuous filament yarns are much more dense thanyarns made from synthetic staple fibers and lack the bulk which provideslightness, covering power, and warmth-giving properties. Production ofyarn from staple fibers, however, is time consuming and requires acomplex series of operations. Recent developments in the textileindustry have provided useful routes for improving the bulk and coveringpower of continuous filament yarns without resorting to conventionalstaple spinning systems.

As disclosed in Breen US. Patents No. 2,783,609, issued March 5, 1957,and No. 2,852,906, issued September 23, 1958, a textured yarn, such asthat sold under the du Pont trademark Taslan, is produced by passingmultifilament yarn through a jet where it is subjected to a turbulentstream of compressible fluid which temporarily separates the filamentsand whips them into a multitude of loops and other convolutions. Whenoperated with unheated compressed air, the filaments are recombinedunder a minimum of tension and twisted together to hold the convolutionsin place in the yarn, since the convolutions are not set in thefilaments. This textured continuous filament yarn has many of thedesirable properties of spun staple yarn. However, the introduction oftwist limits the bulk and limits the production rate to the relativelyslow operating speeds of conventional yarn twisting apparatus, e.g.,uptwisters or downtwisters. Although convolutions can be heat-set in thefilaments by separate after-treatment, as by stearning, to provide abulky, extensible yarn which does not require twist, this considerablyincreases the production cost.

Steam, hot air, or other heated compressible fluid can be used in thejet for bulking yarn and, under proper conditions, stable crimped yarncan be produced directly which does not require twist to hold theconvolutions in place. This process can be operated at much higherspeeds than when a twisting step is required, and produces a moredesirable, much bulkier yarn. A highly desirable stable crimp having arandom, three-dimensional, curvilinear, extensible configuration can beintroduced in the filaments with apparatus and process conditions suchas those disclosed in Breen et al. Canadian Patent No. 651,- 831 issuedNovember 6, 1962. However, a difliculty encountered with low twistjet-crimped, continuous filament yarns is that the convolutions tend tosnarl with those of adjacent yarns and to catch on parts of equipment,particularly during processing into fabric. In accordance with thepresent invention, a way has been found to overcome this difiiculty aspart of the yarn treatment process. An object of the invention is toprovide improvements in the process for jet crimping with heatedcompressible fluid. Other objects will become apparent from thespecification and claims.

In the process of the present invention, bulky yarn, composed ofcontinuous filaments of synthetic linear condensation polymer which havebeen drawn, crimped into 3,143,784 Patented Aug. 11, 1964 iceconvolutions in a turbulent stream of heated compressible fluid andcooled to provide a crimp-set yarn having an elongation at break greaterthan 40% based on elongation occurring after the yarn has been extendedto a length just sufficient to remove the convolutions, is redrawn attemperatures between about 0 C. and C. to about 1.10 to 1.50 times saidextended length. After release of redrawing tension, this redrawn yarnhas the appearance and mechanical processing properties of conventionaluncrimped continuous filament yarn. However, the bulk is recovered whenthe yarn is hot-relaxed, as in conventional boil-off and heat-setting ofwoven or knitted fabric.

The elongation and the extent of redrawing referred to above andelsewhere in the specification and claims is in addition to, anddistinct from, extension resulting solely from removal of crimp or otherconvolutions. Thus, to redraw crimped yarn 1.10 sufiicient tension isapplied to straighten the filaments and the yarn is then stretched toincrease the length an additional 10%.

The bulk yarn can be prepared as disclosed in more detail in Breen etal. Canadian Patent No. 651,831 by feeding drawn yarn through a jetsupplied with steam or hot gas at a temperature of at least C. andforwarding the yarn against a screen which carries the yarn away fromthe jet and supports it until the crimp is set. The bulked yarn can passdirectly from the screen to the redrawing step, or the bulked yarn canbe collected and redrawn subsequently in a separate operation. Thisredrawing step may be accomplished with a yarn drawing apparatuscomprising a means for supplying yarn at a uniform rate, a snubbingelement, a means for applying drawing tension to the yarn, and means forwinding up the drawn yarn.

The invention will be more easily understood by referring to theaccompanying drawing, which is a schematic perspective view of apparatussuitable for carrying out the steps of drawing, bulking and redrawing inaccordance with the principles of this invention.

In the drawing, undrawn yarn 1 is shown passing continuously betweenfeed rolls 2 and 3 around pin 4 to draw roll 5. Several wraps are placedabout the draw roll and idler roll 6. The drawn yarn is then passedcontinuously through guide 7 to jet 8 and crimp set on the screensurface of screen disk 9. The disk is rotated to carry the bulked yarnaway from the jet stream, and the bulked yarn is withdrawn from the diskthrough guide 10 at a subsequent position in its rotation by take-offrolls 1?. and 12. From the take-off rolls, the bulky yarn is passedaround pin 13 to redraw roll 14. If desired, the pin 13 may be omittedwith no deleterious etiects. \Vhen it is des red to heat the yarn, thiscan be done by use of a heated pin at 13. It is preferred that a pin beused and that an unheated pin be used, i.e., that redrawing be carriedout at room temperature. Several wraps are taken around redraw roll 14and idler roll 15, the redrawn yarn is then passed continuously overguide roll 36 and through traversing guide 17 to package 13 driven byroll 19.

Normally, draw ratios of 1.1 and higher are necessary in order to removethe bulk from the yarn. At draw ratios of up to 1.03, some bu k remains;while at draw ratios of 1.1 and higher, the yarn becomes filament-likein appearance. At draw ratios in excess of 1.5, the yarns begin toexhibit loss of bulk on subsequent boil-off. Draw ratios between 1.1 and1.2 are preferred since the lower draw ratios are attended by lowershrinkage levels.

During drawing, the yarn should not be heated above 130 C. andpreferably not above 115 C. Useful bulk and/ or crimp can be obtainedfrom yarns drawn at temperatures as high as 130 C. However, maximum bulkis realized when the yarn is drawn at temperatures below 115 C., anddrawing temperatures, therefore, will normally range from roomtemperature to approximately 115 C.

During the production of bulked yarns as described above, a mostsurprising shrinkage of the filaments and relaxation of the moleculesmaking up the filaments occur. The dynamic relaxation which occurs inthe hot turbulent fluid of the bulking jet eliminates most of thenon'uniformities from the yarn filaments and, thus, the treated yarnshave much more uniform dyeability; and, in addition, there is a largeincrease in dye receptivity.

The dynamic relaxation is responsible for a considerable amount ofdeorientation of the molecules. In drawing these yarns during thepractice of this invention, the molecules of the fibers are reorientedand, as would be expected, there is a corresponding increase in theshrinkage. However, when these redrawn yarns are boiled off, theresulting fibers possess the same high degree of dyeability possessed bythe original bulk yarn, and there is no discernible difference in theirdyeing uniformity.

The crimp of the bulked yarns is described in the Canadian Patent No.651,831 as a random curvilinear configuration, the useful productshaving a crimp level in excess of crimps per inch. In redrawing thebulked yarns, the crimps are removed in order to improve processabilityof the subsequent product which has the physical appearance of aconventional filament yarn. Most surprisingly, however, when the redrawnyarns are again subjected to shrinkage conditions, the filaments assumetheir original curvilinear configuration with no apparent change incrimp frequency and, most preferably, have a crimp frequency of tocrimps per inch.

The term synthetic linear condensation polymer used above refers tofiber-forming linear polyesters and polyamides.

By polyesters is meant crystallizable linear condensation polymerscontaining in the polymer chain carbonyloxy linking radicals Polymerscontaining oxycarbonyloxy radicals are comprehended within this group.The polymers should be of fiber-forming molecular weight. Copolyesters,terpolyesters, and the like, are intended to be comprehended within theterm polyesters.

Examples of crystallizable, linear condensation polymers includepolyethylene terephthalate, polyethylene terephthalate/isophthalate(85/15), polyethylene terephthalate/S-(sodium sulfo) isophthalate(97/3), poly(phexahydroxylene terephthalate), poly(diphenylolpropaneisophthalate), poly(diphenylolpropane carbonate), the polyethylenenaphthalene dicarboxylates (especially those derived from the 2,6- and2,7-isomers) and poly(mphenylene isophthalate) as Well as many others.

Suitable polyamides are those melt-spinnable synthetic linear polyamideswhich are prepared from polymerizable monoamino monocarboxylic acids ortheir amideforming derivatives, or from suitable diamines and suitabledicarboxylic acids or from amide-forming derivatives of these compounds.Typical of such polyamides are those formed from an aliphatic diamineand an aliphatic acid containing the repeating unit linkage. Especiallyuseful polyamides are those in which -X and Y are (CH where n is aninteger of 4 from 0 to 12 inclusive; X and Y may be the same ordifferent. Polyhexamethylene adipamide, polycaproamide (i.e., 66 and 6nylons) and polyundecanoamide are typical. Other suitable polyamides arethose having the repeating structure wherein -A is a divalent aromaticradical and X and Z are as previously defined. Polyhexamethyleneisophthalamide is illustrative of such polymers. Additionally polyamideshaving repeating units such as Where B is divalent flkaryl (such asxylene) may be used provided that only the melt spinnable polymers andcopolymers are intended. Another class of suitable polyamides containingother than aromatic intracarbonamide repeating units are those preparedfrom piperazine, such as those from piperazine and adipic acid, and thelike. Melt-spinnable copolymers wherein the amide linkage is thepredominant linkage and polyamide mixtures are also useful.

The process of this invention produces a yarn that will show a grossincrease in bulk on subsequent boil-ofi'. A comparison of the boil-01fdenier to the redrawn denier is a crude indication of the bulk increase.However, a better measure of bulk can be obtained by determining thevolume of a definite weight of fabric while under pressure. For thepurpose of this invention, bulk is, therefore, measured under a pressureof 3.4 lbs/sq. in. Before testing, the fabric is preconditioned at 55i5C. for a minimum of two hours and is then conditioned for 16 hours atrelative humidity at 21 C. Fabric samples of known area are thenweighed. The thickness of the sample under a pressure of 3.4 pounds persquare inch is then determined. The volume in cubic centimeters is thencalculated, and this value divided by the weight of the sample in gramsis the specific volume (cc./g.).

EXAMPLE I A polyethylene terephthalate/S-(sodium sulfo)-isophthalate(98/2) yarn having a trilobal cross-section is drawn to denier andbulked according to Canadian Patent No. 651,831 at a steam temperatureof 500 F. and pressure of 50 p.s.i.g. to give a denier of 117 and abreak elongation of The bulked yarn is forwarded by feed rolls to anunheated draw pin 13 and around redraw rolls 14 and 15 as illustrated inthe figure of the accompanying drawing. Three wraps are taken around theredraw rolls to prevent slippage. The yarn is redrawn 1.123 and wound upat a speed of 454 y.p.m. The redrawn yarn has a denier of 105, atenacity of 2.0 g./d., an elongation of 64%, a yield point of 0.82g./d., an initial modulus of 47 g./d., and a boil-off shrinkage of10.0%. The redrawn yarn is downtwisted to 3 t.p.i. twist and woven intoa plain fabric. The woven fabric has a loom count of 64 by 64 ends/inch,a fabric weight of 1.85 0unces/yd. and a fabric bulk before finishing of1.5 cc./ g. The fabric is boiled off at C. for 15 minutes and heat setat C. After boil-off and heat setting, the fabric has a loom count of'72 by 74 ends/inch, a fabric weight of 2.25 ounces/yd. and a fabricbulk of 2.75 cc./ g. The aesthetics of the finished fabric areexcellent.

Specimens of the drawn, the bulked, and the redrawn yarn are dyed in a0.016% Latyl Yellow 3G bath at 100 C. for 25 minutes. Dye absorption isfound to be 0.4% for the initial drawn yarn, 1.0% for the bulked yarn,and 1.0% for the redrawn yarn, showing that there is no change in thedyeability as a result of the redrawing. Dyeing uniformity of the bulkedand of the redrawn yarn is equivalent and both have dyeing uniformitysuperior to the drawn yarn.

EXAMPLE II Apparatus for processing yarn is set up as shown in thedrawing. A 40-denier drawn yarn of polyethylene terephthalate having 27filaments is delivered from rolls 5 and 6 at 100 yds./min. to thebulking jet 8, whence it is deposited on screen 9. The steam temperaturein the jet is 293 C. and the pressure is 50 psig. The yarn is carriedalong on the screen at 50 y.p.m. until it is cooled and the crimp isset. The bulked yarn, having a denier of 67 and a break elongation of95%, continues around pin 13 and over rolls 14 and 15 for redrawing. Theyarn is drawn at a draw ratio of 1.12 at room temperature and wound upat 589 yds./min. The redrawn yarn has a denier of 60, a tenacity of 2.7g./d., an elongation of 64%, a yield point of 0.80 g./d., an initialmodulus of 47 g./d., and a boil-ofi shrinkage of 10.0%.

Specimens of the drawn, the bulked and the redrawn yarn are dyed at 100C. in a 0.016% Latyl Yellow 36 bath. Dye absorption is found to be 0.2%for the drawn yarn, 0.4% for the bulked yarn, and 0.4% for the redrawnyarn, showing that there has been no change in the dyeability as aresult of the redrawing process.

Conversion of this yarn to fabric and subsequent boiloff as in Example Ishows a bulk of 2.9 cc./ g. vs. a bulk before boil-off of 1.8 cc./ g.

A second run at a draw ratio of 1.42 gives equivalent results.

EXAMPLE III A 10-filament polyhexamethylene adipamide yarn is drawn andsteam bulked as in Example I to a denier of 105 and a break elongationof 64%, and is then redrawn with the arrangement of pin and draw rollsdescribed. The yarn is drawn 1.16 at 26 C. and wound up at 454 y.p.m.The redrawn yarn has a denier of 91, a tenacity of 3.5 g./d., and anelongation of 43%, and a boil-off shrinkage of 16%. Conversion of thisyarn to fabric and subsequent boil-off shows a bulk of 2.8 cc./g. versusa bulk before boil-oft of 1.6 cc./ g.

Repeating the above experiment, except that the yarn is drawn 1.38 givesa yarn having a bulk of 2.8 cc./g. after being boiled-off.

EXAMPLE 1V Yarn is prepared as in Example 1 except that the draw pin 13is heated. In this example, 6 runs, A through F, are made attemperatures ranging from 43 C. to 160 C. Specimens prepared at eachtemperature are woven into a satin ribbon construction. Fabric samplesare finished as described above and the efiect of the redrawingtemperature on bulk development is determined. The results, tabulated inTable 1, show that very little bulk is obtained by redrawing at 160 C.and that, while useable bulk is obtained at temperatures as high as 130C., optimum bulk is obtained at temperatures below 112 C.

Table 1 Specific Volume (cc.lg.) Draw pin Run Temp.

C 0.) Before After Boilofi Boil-0E Since many difierent embodiments ofthe invention may be made without departing from the spirit and scopethereof, it is to be understood that the invention is not limited by thespecific illustrations except to the extent defined in the followingclaims.

I claim:

1. In the production of bulky yarn from continuous filaments ofsynthetic linear condensation polymer by drawing the filaments, crimpingthe filaments in a turbulent stream of heated compressible fluid toimpart a random, three-dimensional, curvilinear, extensibleconfiguration, and cooling the filaments to set the crimp, theimprovement of conducting said process to provide bulky, crimped yarnhaving an elongation at break greater than 40%, based on elongationoccurring after the yarn has been extended to a length just sufficientto remove the crimp, and redrawing the yarn at temperatures between 0 C.and 130 C. to 1.10 to 1.50 times said extended length to provide a yarnhaving the appearance and mechanical processing properties of uncn'mpedyarn but which recovers the crimp when hot-relaxed.

2. A process as defined in claim 1 wherein said bulky yarn is redrawn to1.1 to 1.2 times said extended length.

3. A process as defined in claim 1 wherein said bulky yarn is redrawn attemperatures between room temperature and C.

4. A process as defined in claim 1 wherein said yarn is composed ofpolyethylene terephthalate and is redrawn to 1.1 to 1.2 times saidextended length While at a temperature of 20 to 112 C.

5. A process as defined in claim 1 wherein said yarn is composed ofpolyhexamethylene adipamide and is redrawn to 1.1 to 1.2 times saidextended length while substantially unheated.

References Cited in the file of this patent UNITED STATES PATENTS3,017,685 I-Ieberlein Jan. 23, 1962 3,055,080 Claussen et al Sept. 25,1962 FOREIGN PATENTS 636,054 Canada Feb. 6, 1962 1,225,587 France Feb.15, 1960

1. IN THE PRODUCTION OF BULKY YARN FROM CONTINUOUS FILAMENTS OFSYNTHETIC LINEAR CONDENSATION POLYMER BY DRAWING THE FILAMENTS, CRIMPINGTHE FILAMENTS IN A TURBULENT STREAM OF HEATED COMPRESSIBLE FLUID TOIMPART A RANDOM, THREE-DIMENSIONAL, CURVILINEAR, EXTENSIBLECONFIGURATION, AND COOLING THE FILAMENTS TO SET THE CRIMP, THEIMPROVEMENT OF CONDUCTING SAID PROCESS TO PROVIDE BULKY, CRIMPED YARNHAVING AN ELONGATION AT BREAK GREATER THAN 40%, BASED ON ELONGATIONOCCURRING AFTER THE YARN HAS BEEN EXTENDED TO A LENGTH JUST SUFFICIENTTO REMOVE THE CRIMP, AND REDRAWING THE YARN AT TEMPERATURES BETWEEN 0*C. AND 130* C. TO 1.10 TO 1.50 TIMES SAID EXTENDED LENGTH TO PROVIDE AYARN HAVING THE APPEARANCE AND ME-